1. Field of the Invention
The present invention relates to a magnetic head for the purpose of reading an information signal that has been recorded onto a magnetic recording medium or writing an information signal onto a magnetic recording medium, using a magnetoresistive effect, and also to a method of recording and playback which uses the above-noted magnetic head.
2. Description of Related Art
The use of a magnetoresistive effect type of reading transducer for the purpose detecting magnetic signal information that has been recorded onto a magnetic recording medium has been known in the past.
In the case of using this magnetoresistive effect type reading transducer as a magnetic head, in order to maintain linearity in the operating region, and in order both to achieve a single magnetic domain in the construction of a magnetoresistive film (hereinafter referred to as an MR film) and to suppress Barkhausen noise, it was known to be necessary in particular to apply two types of bias magnetic fields to the MR film.
For example, as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 52-062417, one method is to apply a magnetic field in a direction that is perpendicular to the easy magnetization axis of the MR film, this being known as transversal bias.
This transversal bias, for example as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 52-062417, is obtained from a soft magnetic film (hereinafter referred to a as soft adjacent layer or SAL) which is disposed on the MR film with an intervening a non-magnetic film.
Additionally, as disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 62-40610, there is the application of a magnetic field that is horizontal with respect to the easy magnetization axis of the MR film, this being known as the longitudinal bias. This longitudinal bias is obtained by means of exchange coupling between the MR film and an antiferromagnetic film which is disposed so that the antiferromagnetic film makes contact with at least a part of the MR film.
However, in the case of forming patterning by etching the MR film and SAL, closure domains and magnetic anisotropy occur due to the shape thereof, causing Barkhausen jump and SAL reversal.
For example, in the case in which the MR film and the SAL shape is made long in the longitudinal bias direction, shape magnetic anisotropy increases the anisotropy in the longitudinal bias direction, thereby preventing saturation of the SAL in the transversal bias direction.
As a result, in the signal magnetic field from the medium as well there is a tendency for the SAL to exhibit reversal, this causing noise on the playback signal. In a different example, in the case in which the MR film and SAL shapes are made rectangular, a multiple magnetic domain structure occurs at the corners of this MR film, this causing Barkhausen jump.
Additionally, if the contact between the MR film and the antiferromagnetic film is insufficient, it is not possible to obtain sufficient exchange coupling, resulting in a multiple magnetic domain structure in the MR film, this causing Barkhausen jump.
In the Japanese Unexamined Patent Publication (KOKAI) No. 7-129926, there is discovery of technology that, in establishing the relationship between the thicknesses of the magnetoresistive film and the SAL and the saturation magnetization, solves the above-noted problem. However, even in this structure it is difficult to eliminate Barkhausen noise entirely.
In view of the above-described drawbacks in the prior art, an object of the present invention is to provide a magnetic head which is a magnetoresistive effect type reading transducer that improves on the above-noted problems, and which not only has magnetic stability, but also has superior playback characteristics.